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Journal of Indian Society of Pedodontics and Preventive Dentistry Official publication of Indian Society of Pedodontics and Preventive Dentistry
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Year : 2019  |  Volume : 37  |  Issue : 3  |  Page : 271-274

Scanning electron microscopic observation of primary tooth dentin following final irrigation with 95% ethanol: An in vitro study

1 Department of Pediatric and Preventive Dentistry, Nair Hospital Dental College, Mumbai, Maharashtra, India
2 Department of Pediatric and Preventive Dentistry, Government Dental College and Hospital, Mumbai, Maharashtra, India
3 Department of Pediatric and Preventive Dentistry, Nair Hospital Dental College, Mumbai,Maharashtra, India
4 Department of Pediatric and Preventive Dentistry, Saraswati Dhanwantari Dental College and Hospital, Parbhani, Maharashtra, India
5 Department of Conservative Dentistry and Endodontics, Nair Hospital Dental College, Mumbai, Maharashtra, India

Date of Web Publication30-Sep-2019

Correspondence Address:
Dr. Adesh Kakade
Department of Pediatric and Preventive Dentistry, Nair Hospital Dental College, Mumbai, Maharashtra
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/JISPPD.JISPPD_113_19

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Background: The beneficial effects of irrigants during endodontic treatment are well known; however, it may have some deleterious effects on the internal root canal wall, thereby altering its physical properties. Aim: The purpose of the study was to assess the effect of 95% ethanol on morphological characteristics of primary root dentin. Materials and Methods: Biomechanical preparation was done in twenty extracted single-rooted primary anterior teeth using Rotary ProTaper Universal System. Samples were divided into two groups based on the final irrigation protocol: nonalcohol group (NAG) and alcohol group (AG). 3% sodium hypochlorite and 17% ethylenediaminetetraacetic acid were used for irrigation in both the groups, whereas 95% ethanol was used as a final irrigant in AG. After the treatment, these teeth were longitudinally sectioned and studied under the scanning electron microscope (SEM). Results: SEM observation of NAG showed scattered debris with unaffected morphology of dentinal tubules (DT). In AG, DT showed severe erosion with the loss of peritubular and intertubular dentin. Conclusion: A final rinse with 95% ethanol can change the morphology of the internal root surface and aid in smear layer removal in primary teeth.

Keywords: Dentinal erosion, endodontic irrigation, ethanol, intertubular dentin, primary teeth

How to cite this article:
Santosh A, Kakade A, Mali S, Lalwani R, Badnaware S, Deshmukh B, Shetty H. Scanning electron microscopic observation of primary tooth dentin following final irrigation with 95% ethanol: An in vitro study. J Indian Soc Pedod Prev Dent 2019;37:271-4

How to cite this URL:
Santosh A, Kakade A, Mali S, Lalwani R, Badnaware S, Deshmukh B, Shetty H. Scanning electron microscopic observation of primary tooth dentin following final irrigation with 95% ethanol: An in vitro study. J Indian Soc Pedod Prev Dent [serial online] 2019 [cited 2022 Aug 17];37:271-4. Available from: http://www.jisppd.com/text.asp?2019/37/3/271/268174

   Introduction Top

The main purpose of the root canal filling is to seal the root canal system three dimensionally. In contrast to endodontic therapy of permanent teeth which consists of root canals coated with a sealer and filled with a central hardcore nonresorbable material such as gutta-percha, primary teeth are filled with a sealer that is used as an obturating material.[1] Ideally, a sealer/obturating material should not only seal the irregularities in root canal such as accessory canals and fins but also penetrate deeper into dentinal tubules (DT) to have its therapeutic effects. Hence, it is imperative that DT are open and not blocked by smear layer, precipitates, or any other debris.[2] Moisture present in the canal can also prevent adaptation and penetration of sealer/obturating material. Numerous techniques such as paper points, alcohol, and Luer Vacuum Adapter have been used to remove the residual moisture from the root canal prior to obturation.[3]

Alcohol is known for its dehydrating effect which makes it effective in drying the canals before obturation.[4] A final rinse with 95% ethanol is known to cause increased sealer penetration into the DT.[4] This dehydrating and surfactant action of ethanol can be utilized to dry the canals to facilitate root canal filling.[5] Beneficial effects and properties of alcohol have been described by various authors, but the effect that alcohol has on the internal surface of the primary root canal system has not been studied.[3],[4],[6],[7] The purpose of this study was to evaluate the effect of 95% ethanol as a final irrigant on the internal root canal surface of primary teeth.

   Materials And Methods Top

The study protocol was approved by the institutional review board (EC-73/PEDO-06ND/2017). Twenty carious nonrestorable single-rooted primary anterior teeth with a minimum root length of 10 mm were extracted and selected for the study. The extracted teeth were immersed in 10% formalin for 7 days for disinfection. Pre-radiographic evaluation of the teeth was done to detect any morphological defects. The extracted teeth were decoronated at the cementoenamel junction, and working length was determined by inserting a 10 number K-File (Dentsply Mailefer, Ballaigues, Switzerland) 0.5 mm short of the apex. The root canals were then prepared to size F1 using Rotary ProTaper Universal System (Dentsply Mailefer, Ballaigues, Switzerland). All specimens were irrigated with 3 ml of 3% sodium hypochlorite (NaOCl) with a 30-gauge side venting needle after each instrumentation. The teeth were then randomly divided into two experimental groups, each consisting of 10 teeth that underwent the final irrigation protocol as described below:

  • Nonalcohol group (NAG): Irrigation was carried out with 1 ml of 17% ethylenediaminetetraacetic acid (EDTA) (Pulpdent Corp, Watertown, MA)
  • Alcohol group (AG): Irrigation was carried out with 1 ml of 17% EDTA (Pulpdent Corp, Watertown, MA) followed by a final rinse with 1 ml of 95% ethanol for 1 min.

Longitudinal grooves were made along the outer surface of the root canals without entering the main canal, and the teeth were then split open to obtain two uniform sections. Specimens were observed under the scanning electron microscope (SEM), and photomicrographs were taken at 1, 3, and 6 mm from the apex representing the apical, middle, and coronal sections, respectively.

   Results Top

Nonalcohol group

SEM analysis of the NAG showed individual DT which were clearly observed in the cervical and middle third regions, but a considerable amount of smear layer was observed in the apical third. The peritubular and intertubular dentin appeared to be smooth and flat [Figure 1].
Figure 1: The scanning electron microscopic images of nonalcohol group. (a) Coronal third, (b) Middle third, and (c) Apical third (×4000) showing scattered debris and intact morphology of dentinal tubules

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Alcohol group

Severe erosion of DT was observed in all three sections. One characteristic feature observed was the loss of peritubular and intertubular dentin. The severity of erosion decreased from cervical to apical direction. The conjugation of DT was observed. This conjugation involved mainly two DT, but in the coronal section, we observed a conjugation of three or more DT [Figure 2].
Figure 2: The scanning electron microscopic images of alcohol group. (a) Coronal third, (b) Middle third, and (c) Apical third (×4000) showing erosion of dentinal tubules with loss of peritubular and intertubular dentin

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   Discussion Top

Various endodontic irrigating solutions have been recommended for the efficient removal of the smear layer from the internal surface of the root canal wall.[8] A combination of NaOCl and EDTA has been proven to remove smear layer, but it generally fails to do so in the apical areas.[9] An extensive literature on final irrigation regimens is available to remove the smear layer as well as to enlarge the DT and to increase its wettability.[4] Chemicals such as ethanol, isopropyl alcohol, Mixture of Doxycycline, Citric acid and a detergent (MTAD), citric acid, EDTA, and maleic acid have been used as final irrigants.[10],[11],[12],[13] Alcohol has been advocated as the final irrigant in permanent teeth by a number of authors to dry the root canals prior to obturation since residual moisture may prevent adaptation and penetration of obturating materials.[3],[4],[7] Ethanol is considered as a dehydrating medium. Following dehydration with ethanol, dentin becomes hydrophobic making it more compatible with endodontic sealers. Stevens et al., demonstrated that a final rinse with 95% ethanol improved the penetration of sealers in DT.[4] The tensioactive property of ethanol has been shown to improve the flow of irrigants into DT in vitro by lessening the surface tension of NaOCl and EDTA.[14]

Severe dentinal erosion was observed in cervical, middle, and apical thirds along with complete removal of smear layer from the apical third of root canals in AG. We attribute this absence of smear layer to dentinal erosion. All regions showed the conjugation of DT, with severe conjugation in the cervical section as compared to middle and apical sections. In the NAG, minimal dentinal erosion was observed because the absence of ethanol rinse prevented the enhanced penetration of irrigants into DT. We hypothesize that the action of NaOCl and EDTA was accentuated by ethanol, causing severe erosion in AG. In a study, Niu et al., reported an accelerated rate of dentinal erosion describing it as a result of hyper-decalcification induced due to EDTA.[15] Calt and Serper reported that dentinal erosion was noted on instrumented root canal walls when irrigated with 10 ml of 17% EDTA followed by 10 ml of 5% NaOCl.[16]

An increased rate of dentinal erosion in AG was observed because our study sample comprised primary teeth as compared to other studies on permanent teeth.[15] The erosion of DT led to conjugation of two or more tubules resulting in a characteristic “dumbbell“-shaped appearance with two DT, a triangular appearance with three DT and irregular shape when more than three DT were conjugated [Figure 3]. Primary tooth dentin has higher collagenous content as compared to permanent tooth dentin. The probable reasons for erosion and the characteristic shape of conjugated DT could be because of higher organic content in primary teeth and the orientation of collagen fibers in and around the peritubular and intertubular dentin.[17],[18] Peritubular dentin is a highly mineralized tissue that surrounds the individual DT. Adjacent DT are separated by intertubular dentin, which is 9% less mineralized than the peritubular dentin.[19] This difference in composition is reflected in the different rates of dissolution following final irrigation of the instrumented root canal. Kinney JH observed that initially both peritubular and intertubular dentin dissolve at the same rate, but after 1 min, the peritubular dentin dissolves further, while the intertubular dentin appears stable.[20] In our study, we observed that the DT orifices were enlarged at the expense of peritubular and intertubular dentin.
Figure 3: Schematic representation of dentinal tubule erosion: (a) Single dentinal tubules showing enlarged tubule orifice, (b) Conjugation of two dentinal tubules showing dumbbell appearance, (c) Conjugation of three dentinal tubules showing triangular appearance, and (d) Conjugation of more than three dentinal tubules showing irregular appearance

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There is a plethora of literature available on irrigation and its effect on dentin, microorganisms, and pulp. However, most of these studies have been done on permanent teeth. Very few studies have used primary teeth.[11],[12],[13] Hence, it would be inappropriate to directly extrapolate the results of these studies onto primary teeth. The clinical significance of final rinse with 95% ethanol was smear-free internal root canal surface in AG as compared to the NAG, but it was associated with a considerable amount of dentinal erosion. The clinical implications of dentinal erosion on the success of endodontics need to be assessed, especially the penetration of the endodontic irrigants, sealer, or obturating material into the DT and its effect on the physical properties of dentin. It can be inferred that 95% ethanol can effectively remove smear layer from the root canal. However, it can significantly change the morphology of DT when used in combination with NaOCl and EDTA.

   Conclusion Top

Based on the results of this study, it can be inferred that a final rinse with 95% ethanol can change the morphology of the internal root surface and aid in smear layer removal in primary teeth.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

   References Top

Evans JT, Simon JH. Evaluation of the apical seal produced by injected thermoplasticized gutta-percha in the absence of smear layer and root canal sealer. J Endod 1986;12:100-7.  Back to cited text no. 1
Nagas E, Uyanik MO, Eymirli A, Cehreli ZC, Vallittu PK, Lassila LV, et al. Dentin moisture conditions affect the adhesion of root canal sealers. J Endod 2012;38:240-4.  Back to cited text no. 2
Engel GT, Goodell GG, McClanahan SB. Sealer penetration and apical microleakage in smear-free dentin after a final rinse with either 70% isopropyl alcohol or peridex. J Endod 2005;31:620-3.  Back to cited text no. 3
Stevens RW, Strother JM, McClanahan SB. Leakage and sealer penetration in smear-free dentin after a final rinse with 95% ethanol. J Endod 2006;32:785-8.  Back to cited text no. 4
Thiruvenkadam G, Asokan S, John B, Priya PG. Effect of 95% ethanol as a final irrigant before root canal obturation in primary teeth: An in vitro study. Int J Clin Pediatr Dent 2016;9:21-4.  Back to cited text no. 5
Nalla RK, Kinney JH, Tomsia AP, Ritchie RO. Role of alcohol in the fracture resistance of teeth. J Dent Res 2006;85:1022-6.  Back to cited text no. 6
Wilcox LR, Wiemann AH. Effect of a final alcohol rinse on sealer coverage of obturated root canals. J Endod 1995;21:256-8.  Back to cited text no. 7
Kandil HE, Labib AH, Alhadainy HA. Effect of different irrigant solutions on microhardness and smear layer removal of root canal dentin. Tanta Dent J 2014;11:1-11.  Back to cited text no. 8
Fraser JG. Chelating agents: Their softening effect on root canal dentin. Oral Surg Oral Med Oral Pathol 1974;37:803-11.  Back to cited text no. 9
Torabinejad M, Khademi AA, Babagoli J, Cho Y, Johnson WB, Bozhilov K, et al. A new solution for the removal of the smear layer. J Endod 2003;29:170-5.  Back to cited text no. 10
Götze Gda R, Cunha CB, Primo LS, Maia LC. Effect of the sodium hypochlorite and citric acid association on smear layer removal of primary molars. Braz Oral Res 2005;19:261-6.  Back to cited text no. 11
Ximenes M, Triches TC, Beltrame AP, Hilgert LA, Cardoso M. Effect of endodontic irrigation with 1% sodium hypochlorite and 17% EDTA on primary teeth: A scanning electron microscope analysis. Gen Dent 2013;61:24-7.  Back to cited text no. 12
Nelson-Filho P, Leite Gde A, Fernandes PM, da Silva RA, Rueda JC. Efficacy of smearClear and ethylenediaminetetraacetic acid for smear layer removal in primary teeth. J Dent Child (Chic) 2009;76:74-7.  Back to cited text no. 13
Cunningham WT, Cole JS 3rd, Balekjian AY. Effect of alcohol on the spreading ability of sodium hypochlorite endodontic irrigant. Oral Surg Oral Med Oral Pathol 1982;54:333-5.  Back to cited text no. 14
Niu W, Yoshioka T, Kobayashi C, Suda H. A scanning electron microscopic study of dentinal erosion by final irrigation with EDTA and NaOCl solutions. Int Endod J 2002;35:934-9.  Back to cited text no. 15
Calt S, Serper A. Smear layer removal by EGTA. J Endod 2000;26:459-61.  Back to cited text no. 16
Bird MJ, French EL, Woodside MR, Morrison MI, Hodge HC. Chemical analyses of deciduous enamel and dentin. J Dent Res 1940;19:413-23.  Back to cited text no. 17
Xu C, Wang Y. Chemical composition and structure of peritubular and intertubular human dentine revisited. Arch Oral Biol 2012;57:383-91.  Back to cited text no. 18
Kumar GS. Orban's Oral Histology & Embryology. Gurgaon, Haryana, India: Elsevier Health Sciences; 2014.  Back to cited text no. 19
Kinney JH, Balooch M, Haupt Jr DL, Marshall SJ, Marshall Jr GW. Mineral distribution and dimensional changes in human dentin during demineralization. J Dent Res 1995;74:1179-84.  Back to cited text no. 20


  [Figure 1], [Figure 2], [Figure 3]


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